Location: Diet, Genomics and Immunology Laboratory2010 Annual Report
1a. Objectives (from AD-416)
The overall goal of the project is to elucidate the molecular and cellular mechanisms that respond to selected health promoting food components to reduce the risk of chronic diseases such as cancers and obesity. A secondary aim is to explore the utility of a porcine model to test the effect of health maintenance via diet and identify resulting biomarkers that reflect health status. Objective 1. Elucidate biological activities of health promoting phytochemicals from grape, soy, and cruciferous vegetables against development of breast and prostate cancer. Objective 2. Identify molecular targets and mechanisms of action of health promoting food components in animal or in vitro models of cancer and obesity. Objective 3. Ascertain the effects of specific probiotic strains in appropriate animal models of obesity. Objective 4. Identify plant polyphenols and probiotics that affect adipocyte numbers, size, and fat accumulation, and the regulation of proinflammatory mRNA stability by tristetraprolin. Objective 5. Tie together obesity, inflammation, and cancer mechanistically in appropriate animal or in vitro models.
1b. Approach (from AD-416)
Studies will evaluate if phytoalexins structurally similar to resveratrol exerts similar anti-prostate cancer effects; if soy phytoalexin glyceollins exert anti-prostate cancer effects; if phytochemicals modulate LXR-mediated pathways in prostate epithelial cells and modulate LXR-mediated pathways in macrophage. Other studies will determine if probiotic bacterial strains differ in their protective effects against chronic diseases related to obesity; regulate adipocyte numbers, size, and fat accumulation associated with the anti-inflammatory protein tristetraprolin (TTP); if obesity alters the macrophage phenotype and function in adipose tissue, colon, breast, and prostate following increased localized inflammation; and if broccoli-derived phytochemicals modulate LXR-responsive pathways in vivo. The studies will involve in vitro cell culture approaches confirmed by rodent and pig animal models.
3. Progress Report
Feeding a high fat/high fructose/high cholesterol (HF/HFr/HC) diet to juvenile Ossabaw pigs induced obesity and insulin resistance, visceral adipose expansion, hypertriglyceridemia, and increased LDL:HDL and serum cholesterol levels indicative of metabolic syndrome. Inflammation related to obesity contributes to poor health. Certain strains of probiotic bacteria, including Bifidobacterium lactis Bb12 (Bb12), reduce inflammation. To test the hypothesis that Bb12 could reduce inflammation, three groups of Ossabaw pigs were maintained on 1) a HF/HFr/HC diet and fed daily 2 x 1010 cfu of Bb12, 2) a HF/HFr/HC diet and fed a probiotic-free placebo, or 3) maintained on a control basal diet. The HF/HFr/HC diet induced a significant increase in intestinal coliform bacteria and a decrease in Bifidobacterium species in feces compared to pigs on the basal diet, and this effect was reversed in pigs fed the probiotic. Analysis of the intestinal microbiota by molecular pyrosequencing showed diet-dependent shifts in bacterial populations. Analysis of the local host response showed a 7-fold increase in leptin gene expression in adipocytes isolated from pigs fed the HF/HFr/HC diet and given the placebo that was absent in pigs fed the probiotic. Differences in leptin receptor gene expression in the brain were also observed. In a separate study, diet-derived compounds were screened for anti-cancer activity using cell culture-based models. Several phytoalexins, plant phytochemicals activated by stress, inhibited the androgen-responsive human prostate cancer cell line LNCaP. Five diet-derived phytoalexins structurally similar to resveratrol, a cancer protective phytoalexin found in grape skin, exerted differential effects on LNCaP cell growth, cell cycle, and programmed cell death (apoptosis). A derivative compound, trans-resveratrol trimethylether, was the most potent among those tested because it blocked LNCaP cell cycle (G2/M) and induced apoptosis. The effects of these compounds on cell cycle correlated with induction of the cyclin-dependent kinase inhibitor 1A and B mRNA levels, inhibited both androgen- and estrogen-mediated signaling pathways, and provided mechanistic information on how resveratrol and its analogs contribute to anti-prostate cancer cell activity. In another cell culture study, the effects of phytochemcials on the liver-x-receptor (LXR) responsive genes ABCA1 and ABCG1 that regulate cellular cholesterol efflux pumps were examined. Several phytochemicals, including resveratrol, soy-derived genistein and glyceollins, and broccoli-derived 3’, 3’ diindolylmethane, induced ABCA1 and ABCG1 mRNA, supporting the hypothesis that phytochemicals increase the removal of cholesterol from cells. Because cholesterol is a promoter of prostate cancer and obesity-related inflammation, this observation helps explain the health protective effect of phytochemicals.